U.S. patent application number 11/468604 was filed with the patent office on 2007-04-05 for device for treating mitral valve regurgitation.
This patent application is currently assigned to Medtronic Vascular, Inc.. Invention is credited to Eliot F. Bloom, Michael Finney, Raymond Godaire, Nasser Rafiee.
Application Number | 20070078297 11/468604 |
Document ID | / |
Family ID | 37885146 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070078297 |
Kind Code |
A1 |
Rafiee; Nasser ; et
al. |
April 5, 2007 |
Device for Treating Mitral Valve Regurgitation
Abstract
A system for treating mitral valve regurgitation comprises
tensioning device that can be deployed using a delivery catheter.
The device includes tension member linking a proximal anchor and
distal anchor. The device is constructed from a material having
suitable elastic properties such that the device applies a constant
tension force between the anchors, while stretching or flexing in
response to a heartbeat when positioned across a chamber of a
heart. The anchors may include a plurality of arms. In some
embodiments, the arms may also flex in response to a heart beat.
When positioned across the left ventricle of a heart, the device
can reduce the lateral distance between the walls of the ventricle
and thus allow better coaption of the mitral valve leaflets thereby
reducing mitral regurgitation.
Inventors: |
Rafiee; Nasser; (Andover,
MA) ; Bloom; Eliot F.; (Hopkington, NH) ;
Godaire; Raymond; (Auburn, MA) ; Finney; Michael;
(Beverly, MA) |
Correspondence
Address: |
MEDTRONIC VASCULAR, INC.;IP LEGAL DEPARTMENT
3576 UNOCAL PLACE
SANTA ROSA
CA
95403
US
|
Assignee: |
Medtronic Vascular, Inc.
Santa Rosa
CA
|
Family ID: |
37885146 |
Appl. No.: |
11/468604 |
Filed: |
August 30, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60713299 |
Aug 31, 2005 |
|
|
|
60743349 |
Feb 24, 2006 |
|
|
|
Current U.S.
Class: |
600/37 ; 623/2.1;
623/2.37 |
Current CPC
Class: |
A61B 17/0482 20130101;
A61B 17/0401 20130101; A61B 2017/00867 20130101; A61B 2017/0443
20130101; A61B 2017/00243 20130101; A61F 2/2487 20130101; A61B
2017/06052 20130101; A61B 17/00234 20130101 |
Class at
Publication: |
600/037 ;
623/002.37; 623/002.1 |
International
Class: |
A61F 2/00 20060101
A61F002/00; A61F 2/24 20060101 A61F002/24 |
Claims
1. A device for implanting in a heart chamber to treat mitral valve
regurgitation by reducing the lateral distance between the septum
and the free wall of a the heart, the device comprising: an
elongated tension member having a long axis with a distal end and a
proximal end, the tension member being elastic along the long axis
such that when a force is applied, the tension member stretches
from a first length to a second length and when the force is
removed the tension member returns to the first length; a distal
anchor member attached to the distal end of the tension member; and
a proximal anchor member.
2. The device of claim 1 wherein when the device is positioned
across a chamber of a heart the length of the tension member
changes in response to a heartbeat.
3. The device of claim 1 wherein the tension member is a helical
extension spring.
4. The device of claim 3 wherein the tension member is made from a
material selected from a group consisting of a nickel-titanium
alloy, a nickel-cobalt alloy, a cobalt alloy, a thermoset plastic,
a thermoplastic, stainless steel, a biocompatible shape-memory
material, a biocompatible superelastic material, and a combination
thereof.
5. The device of claim 1 wherein the tension member is made from an
elastomeric material.
6. The device of claim 5 wherein the tension member is made from a
material selected from a group consisting of silicone and
urethane.
7. The device of claim 1 wherein at least one of the anchor members
comprises a plurality of flexible arms.
8. The device of claim 1 wherein at least one of the anchor members
comprises an expandable tubular braided portion.
9. The device of claim 1 wherein the anchor members can be
compressed into a delivery configuration and placed within a lumen
of a delivery catheter, and wherein the anchor members self-expand
when they are released from the delivery catheter.
10. The device of claim 1 wherein the proximal anchor is adjustably
attachable and the proximity of the anchors, one to the other can
be adjusted.
11. The device of claim 1 wherein at least a portion of the device
includes a therapeutic agent selected from a group consisting of an
antithrombotic, an anticoagulant, an antibiotic, an
anti-inflammatory, and a combination thereof.
12. A device for implanting in a heart chamber to treat mitral
valve regurgitation by reducing the lateral distance between the
septum and the free wall of a the heart, the device comprising: an
elongated tension member having a long axis with a distal end and a
proximal end, the tension member being elastic along the long axis
such that when a force is applied, the tension member stretches
from a first length to a second length and when the force is
removed the tension member returns to the first length; a distal
anchor member attached to the distal end of the tension member; and
a proximal anchor member attached to the proximal end of the
tension member whereby, when the device is positioned across a
chamber of a heart, the length of the tension member changes in
response to a heartbeat.
13. The device of claim 12 wherein the tension member is a helical
extension spring made from a material selected from a group
consisting of a nickel-titanium alloy, a nickel-cobalt alloy, a
cobalt alloy, a thermoset plastic, a thermoplastic, stainless
steel, a biocompatible shape-memory material, a biocompatible
superelastic material, and a combination thereof.
14. The device of claim 12 wherein the tension member is made from
an elastomeric material selected from a group consisting of
silicone and urethane.
15. The device of claim 12 wherein at least one of the anchor
members comprises a plurality of flexible arms; and the anchor
members can be compressed into a delivery configuration and placed
within a lumen of a delivery catheter, and wherein the anchor
members self-expand when they are released from the delivery
catheter.
16. The device of claim 12 wherein at least one of the anchor
members comprises an expandable tubular braided portion; and the
anchor members can be compressed into a delivery configuration and
placed within a lumen of a delivery catheter, and wherein the
anchor members self-expand when they are released from the delivery
catheter.
17. The device of claim 12 wherein at least a portion of the device
includes a therapeutic agent selected from a group consisting of an
antithrombotic, an anticoagulant, an antibiotic, an
anti-inflammatory, and a combination thereof.
18. A system for treating mitral valve regurgitation, comprising: a
delivery catheter; and a tensioning device received in the delivery
catheter, the tensioning device including an elongated tension
member having a long axis with a distal end and a proximal end, the
tension member being elastic along the long axis such that when a
force is applied, the tension member stretches from a first length
to a second length and when the force is removed the tension member
returns to the first length, a distal anchor member attached to the
distal end of the tension member, and a proximal anchor member; and
whereby the length of the tension member changes in response to a
heartbeat when the device is positioned across a chamber of a
heart.
Description
PRIORITY CLAIM
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) from U.S. Provisional Application No. 60/713,299,
filed Aug. 31, 2005; and U.S. Provisional Application No.
60/743,349, filed Feb. 24, 2006; the entirety of each of which is
hereby incorporated by reference thereto.
TECHNICAL FIELD
[0002] This invention relates generally to medical devices and
particularly to a system and method for treating mitral valve
regurgitation.
BACKGROUND OF THE INVENTION
[0003] The heart is a four-chambered pump that moves blood
efficiently through the vascular system. Blood enters the heart
through the vena cava and flows into the right atrium. From the
right atrium, blood flows through the tricuspid valve and into the
right ventricle, which then contracts and forces blood through the
pulmonic valve and into the lungs. Oxygenated blood returns from
the lungs and enters the heart through the left atrium and passes
through the bicuspid mitral valve into the left ventricle. The left
ventricle contracts and pumps blood through the aorta valve into
the aorta and to the vascular system.
[0004] The mitral valve consists of two leaflets (anterior and
posterior) attached to a fibrous ring or annulus. In a healthy
heart, the mitral valve leaflets overlap during contraction of the
left ventricle and prevent blood from flowing back into the left
atrium. However, due to various cardiac diseases, the mitral valve
annulus may become distended, causing the leaflets to remain
partially open during ventricular contraction and thus allowing
regurgitation of blood into the left atrium. This results in
reduced ejection volume from the left ventricle, causing the left
ventricle to compensate with a larger stroke volume. The increased
workload eventually results in dilation and hypertrophy of the left
ventricle, further enlarging and distorting the shape of the mitral
valve. If left untreated, the condition may result in cardiac
insufficiency, ventricular failure, and death.
[0005] It is common medical practice to treat mitral valve
regurgitation by valve replacement or repair. Valve replacement
involves an open-heart surgical procedure in which the patients
mitral valve is removed and replaced with an artificial valve. This
is a complex, invasive surgical procedure with the potential for
many complications and a long recovery period.
[0006] Mitral valve repair includes a variety of procedures to
repair or reshape the leaflets to improve closure of the valve
during ventricular contraction. If the mitral valve annulus has
become distended, a common repair procedure involves implanting an
annuloplasty ring on the mitral valve annulus. The annuloplasty
ring generally has a smaller diameter than the annulus, and when
sutured to the annulus, the annuloplasty ring draws the annulus
into a smaller configuration, bringing the mitral valve leaflets
closer together and providing Improved closure during ventricular
contraction.
[0007] Annuloplasty rings may be rigid, flexible, or have both
rigid and flexible segments. Rigid annulopasty rings have the
disadvantage of causing the mitral valve annulus to be rigid and
unable to flex in response to the contractions of the ventricle,
thus inhibiting the normal movement of the mitral valve that is
required for it to function optimally. Flexible annuloplasty rings
are frequently made of Dacron.RTM. fabric and must be sewn to the
annular ring with a line of sutures. This eventually leads to scar
tissue formation and loss of flexibility and function of the mitral
valve. Similarly, combination rings must generally be sutured in
place and also cause scar tissue formation and loss of mitral valve
flexibility and function.
[0008] Annuloplasty rings have been developed that do not require
suturing. U.S. Pat. No. 6,565,603 discloses a combination rigid and
flexible annuloplasty ring that is inserted into the fat pad of the
atrioventricular groove, which surrounds the mitral valve annulus.
Although this device avoids the need for sutures, it must be placed
within the atrioventricular groove with great care to prevent
tissue damage to the heart.
[0009] U.S. Pat. No. 6,569,198 discloses a flexible annuloplasty
ring designed to be inserted into the coronary sinus, which is
located adjacent to and partially surrounds the mitral annulus. The
prosthesis is shortened lengthwise within the coronary sinus to
reduce the size of the mitral annulus. However, the coronary sinus
in a particular individual may not wrap around the heart far enough
to allow effective encircling of the mitral valve, making this
treatment ineffective.
[0010] U.S. Pat. No. 6,210,432 discloses a flexible elongated
device that is inserted into the coronary sinus and adapts to the
shape of the coronary sinus. The device then undergoes a change
that causes it to assume a reduced radius of curvature and, as a
result, causes the radius of curvature of the coronary sinus and
the circumference of the mitral annulus to be reduced. While likely
to be effective for modest changes in the size or shape of the
mitral annulus, this device may cause significant tissue
compression in patients requiring a larger change in the
configuration of the mitral annulus.
[0011] U.S. Pat No. 6,908,478 discloses a flexible elongated device
that is inserted into the coronary sinus and anchored at each end
by a self-expanding, toggle bolt-like anchor that expands and
engages the inner wall of the coronary sinus. Application
WO02/1076284 discloses a similar flexible elongated device that is
inserted into the coronary sinus. This device is anchored at the
distal end by puncturing the wall of the coronary sinus, crossing
the intervening cardiac tissue, and deploying the anchor against
the exterior of the heart in the pericardial space. The proximal
end of the elongated member is anchored against the coronary
ostium, which connects the right atrium and the coronary sinus.
Once anchored at each end, the length of either of the elongated
devices may be adjusted to reduce the curvature of the coronary
sinus and thereby change the configuration of the mitral annulus.
Due to the nature of the anchors, both of these devices may cause
significant damage to the coronary sinus and surrounding cardiac
tissue. Also, leaving a device in the coronary sinus may result in
formation and breaking off of a thrombus that may pass into the
right atrium, right ventricle, and ultimately the lungs, causing a
pulmonary embolism. Another disadvantage is that the coronary sinus
is typically used for placement of a pacing lead, which may be
precluded with the placement of the prosthesis in the coronary
sinus.
[0012] U.S. Pat No. 5,961,440(the contents of which are
incorporated into this section by reference thereto) discloses a
method for calculating the tension in the walls of a heart chamber
(column 10, line 25 to column 11, line 7). It has also been stated
that one can calculate the wall stiffness (in the walls of a heart
chamber) by calculating the change in chamber volume over the
change in pressure within the chamber (.DELTA.V/.DELTA.P).
[0013] U.S. Pat. No. 6,616,684(the '684 patent) discloses splint
assemblies that are positioned transverse the left ventricle to
reduce tension in the walls of a heart chamber, thereby reducing
mitral valve leakage. In one embodiment, the assembly is delivered
through the right ventricle. One end of the assembly is anchored
outside the heart, resting against the outside wall of the left
ventricle, while the other end is anchored within the right
ventricle, against the septal wall. The heart-engaging portions of
the assembly, i.e., the anchors, are essentially flat and lie
snugly against their respective walls. The length of the splint
assembly is either preset or is adjusted to draw the two walls of
the chamber toward each other.
[0014] The splint assembly may be delivered endovascularly, which
offers distinct advantages over open surgery methods. First, a
puncture device is delivered into the right ventricle, advanced
through the septal wall, and anchored to the outer or free wall of
the left ventricle using barbs or threads that are rotated into the
tissue of the free wall. A delivery catheter is then advanced over
the needle, piercing both the septal wall and the free wall of the
ventricle. A tension member is then pushed through the delivery
catheter such that a distal anchor is positioned outside the heart.
The catheter is withdrawn, and a second (proximal) anchor is
advanced over the tension member using a deployment tool and
positioned within the right ventricle against the septal wall. A
tightening device then holds the second anchor in a position so as
to alter the shape of the left ventricle. Excess length of the
tension severed prior to removal. Another device for shortening the
distance between the septal wall of a heart chamber and the free
wall of the chamber can be see in the published U.S. Patent
Application No. 2004/0260317, the contents of which are
incorporated herein by reference.
[0015] One potential problem encountered when using devices of the
type described in the '684 patent is that oversized anchors could
tend to negatively alter the chamber geometry and undersized
anchors may migrate through the heart tissue due to forces exerted
by a beating heart. Both the '684 patent and U.S. Pat. No.
6,537,198 disclose addressing this by properly dimensioning the
anchors for the splint devices disclosed therein. However, it would
be desirable to have devices that addressed the issue of anchor
migration in a manner other than strict dimensioning of the
anchors. Such devices could then be used to treat a variety of
heart sizes and they may even allow treatment on hearts having
injured tissue that may be more susceptible to anchor
migration.
[0016] Therefore, it would be desirable to provide a system and
method for treating mitral valve regurgitation that overcome the
aforementioned and other disadvantages.
SUMMARY OF THE INVENTION
[0017] One aspect of the present invention is a device for treating
mitral valve regurgitation, comprising a tension member and
proximal and distal anchors. The distal anchor is attached to a
distal end of the tension member, and the proximal anchor is
attached to a proximal end of the tether.
[0018] As used herein, the terms "distal" and "proximal" refer to
the location of the referenced element with respect to the treating
clinician during deployment of the device with proximal being
closer to the treating clinician than distal. Additionally, when
used to describe the devices herein, the term "elastic," or
variations thereof, shall be understood to mean the ability to
stretch/distort from a first length to a second length under a
force/load and then return to the first length when the force/load
is removed. Similarly, the term "flexible" or variations thereof
shall be understood to mean the ability to distort/flex from a
first shape to a second shape under a force/load and then return to
the first shape when the force/load is removed. Various embodiments
of the devices of the current invention may be referred to herein
simply as "the device" or the "tensioning device" and both terms
are to be understood to mean the same thing herein.
[0019] The devices described herein comprise a biocompatible
material capable of being preset into a desired shape. Such
materials should be sufficiently elastic and flexible that the
tension member applies a constant tension force between the
anchors, while flexing and/or stretching in response to a heartbeat
when the device is positioned across a chamber of a heart. In some
embodiments, the devices can be constructed from wires of such
materials or braided from such materials, and in others the device
can be cut from tubes of such materials.
[0020] Another aspect of the present invention is a system for
treating mitral valve regurgitation that includes the
above-described tensioning device and further comprises a delivery
catheter. The device is slidably received within a lumen of the
delivery catheter.
[0021] Another aspect of the present invention is a method of
treating mitral valve regurgitation by affecting a mitral valve
annulus. A first wall of a chamber of a heart is pierced. A distal
anchor is engaged with a second wall of the heart chamber. A
proximal anchor is engaged with the first wall of the heart
chamber. A tension member links the proximal and distal anchors
applies a constant tension force to reduce the lateral distance
between the two anchors.
[0022] Devices disclosed herein are advantageous over previously
disclosed devices in that they dampen shock to supporting tissues
and have reduced fatigue relative to other devices, there is no
slack state in which a chord or tensioning member may float around
inside of a heart chamber, the devices can be easier to deploy than
previously disclosed devices, and they can provide a reduction in
thrombus formation compared to previously disclosed devices.
Another advantage over previously disclosed devices is that the
devices disclosed herein are made to be the appropriate length
before they are installed, thus there is no adjustment required
when the device is implanted in a heart.
[0023] The aforementioned and other features and advantages of the
invention will become further apparent from the following detailed
description, read in conjunction with the accompanying drawings,
which are not to scale. The detailed description and drawings are
not to scale and should be viewed as being merely illustrative of
the invention rather than limiting, the scope of the invention
being defined by the appended claims and equivalents thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a side view of one embodiment of a device for
treating mitral regurgitation in accordance with the present
invention;
[0025] FIG. 2 is a side view of the device shown in FIG. 1 in an
elongated state;
[0026] FIGS. 3-5 are side views of additional embodiments of
devices for treating mitral regurgitation as described herein;
[0027] FIG. 5A is a partial schematic view illustrating the
placement of an anchor shown in FIG. 5;
[0028] FIG. 6 is an isometric view of an embodiment of a device for
treating mitral regurgitation in accordance with the present
invention, shown in the context of a system for treating mitral
valve regurgitation in accordance with the present invention, the
tensioning device being completely shown, and a guiding catheter
being shown in cross section;
[0029] FIGS. 7 & 8 are schematic views illustrating the
placement of the tensioning device across a left ventricle, in
accordance with the present invention;
[0030] FIG. 9 is an ideal response curve, for the elongation under
load, of materials used for the devices disclosed herein; and
[0031] FIG. 10 is a flow diagram of one embodiment of a method for
treating mitral valve regurgitation in accordance with the present
invention.
DESCRIPTION OF THE INVENTION
[0032] The invention will now be described in detail below by
referring to the attached drawings, where like numbers refer to
like structures. One aspect of the present invention is a device
for treating mitral valve regurgitation by reducing the lateral
space between the septal wall and the free wall of a heart chamber.
One embodiment of a device, in accordance with the present
invention, is illustrated in FIGS. 1 & 2, which show the device
in a deployed/deployment configuration as opposed to a delivery
configuration as depicted in FIG. 6.
[0033] Tensioning device 100 is designed to be positioned across a
chamber of a heart so that it reduces the distance between the
septum and the free wall of a heart chamber to alter the chamber
geometry and wall tension, thereby reducing valvular regurgitation.
Although described below in the context of treating mitral valve
regurgitation by reducing or limiting lateral distension of the
left ventricle as the heart beats, device 100 may be deployed at
other locations in the heart and is readily adapted to a wide
variety of uses, including treating ischemic or dilated
cardiomyopathy.
[0034] As can be seen in FIG. 1, the device 100 includes a proximal
anchor 115 positioned adjacent to the proximal end of a tension
member 120, and a distal anchor 110 positioned adjacent to the
distal end of the tension member 115. The device is constructed
from an elastic material such that the tension member 120 becomes
elongated (stretches) in response to a heartbeat when the device
100 is positioned across a heart chamber. The embodiment shown in
FIG. 1 is a helical extension spring constructed cut from a tube of
material having the desired elasticity.
[0035] Prior to implantation, a clinician can determine the desired
length of the tension device by determining the distance between
the septum and the free wall, the desired wall tension of the heart
chamber, and the desired distance between the septum and the free
wall using the formulas noted in the background section of this
document and standard visualization techniques. Once desired length
for the device and the desired wall tension/stiffness for the walls
of the heart chamber is determined, a spring constant for the
tension member can be determined for minimum spring compliance such
that the tension member will slightly stretch when the heart beats
but the device will not become too elongated.
[0036] After the desired spring compliance and spring constant are
determined, the spring is designed so that it has the minimum
physical dimensions possible that would allow it to perform as
desired. Thus, a clinician would want a spring having a minimum
outer diameter. For helical coil type springs, a clinician would
try to achieve the minimum material diameter of the material used
to make the coils and the minimum number of coils per inch needed
for the spring to perform as desired.
[0037] It should be noted that the spring constant (k) is
determined using Hooke's Law (F=kx, where F=Force and x=spring
displacement) and the spring compliance is the reciprocal of the
spring constant (compliance=1/k). One embodiment of the current
invention has a compliance of five-percent (5%), while another
embodiment of the invention has a spring compliance of
twenty-percent (20%), and other embodiments of the invention can
have spring compliances in the range of one-percent (1%) to
twenty-five-percent (25%).
[0038] FIG. 2 depicts the device with the tension member in an
elongated state. The state of elongation is exaggerated, relative
to actual elongation when implanted in a heart chamber, to
illustrate the fact that the length of the tension member can
change under load. When the device is implanted in a heart chamber,
the tension member 120 will become slightly elongated as the force
load on the member is increased during diastole and it will
contract to its original shape when the force load decreases during
systole. The distal and proximal anchors of the device 110 &
115 respectively, each have a plurality of extendable arms 111,
112, 117, & 117. In at least one embodiment of the invention,
the arms of at least one of the anchoring sections will also flex
in response to a heart beat to further reduce the stress caused by
the anchors on the chamber walls. Elastic stretching of the tension
member with or without additional flexing of anchor arms, reduces
the risk of the device failing due to structural fatigue, and also
reduces localized compressive pressure on tissue against which the
anchors rest thereby reducing the potential for anchor migration
through the heart chamber walls.
[0039] In the various embodiments described herein, the device
comprises a suitable biocompatible material. Such materials
include, but are not limited to, a nickel-titanium alloy, a
nickel-cobalt alloy, other cobalt alloys, a thermoset plastic, a
thermoplastic, stainless steel, a suitable biocompatible
shape-memory material, a suitable biocompatible super elastic
material, combinations thereof, and the like. In some embodiments
the devices can be constructed from wires of such materials and in
others; the devices can be braided from such materials. In at least
one embodiment, the device is cut from a tube of such materials.
The cross-sectional shape of the coils of such devices can vary
based on the characteristics of the materials and in at least one
embodiment the transverse cross-sectional shape of the material
used to make the spring coils is round.
[0040] In the embodiments depicted in FIGS. 1 through 4, each of
proximal and distal anchors comprises a hub portion having evenly
flexible arms formed therefrom. While these figures show the
devices in side view such that only two arm sections are seen, the
embodiments of devices shown have three arms per anchor. In other
embodiments, the arms may be formed separately from the body of the
anchor and assembled to create an integral whole. Additionally, the
anchors of various embodiments of the invention can include two,
three, four, or more arms.
[0041] During manufacture of at least one embodiment, the arms are
bent outward and heat set or otherwise set such that each of the
arms is self-deploying radially outward at an angle of between 40
and 90 degrees from the longitudinal axis of the anchor when the
anchor is released from a delivery catheter. The length of the arms
is generally calculated so that the diameter of a circle that would
just cover the expanded anchor is five times the diameter of the
piercing tube/catheter (634 of FIG. 6) that is used to deliver the
device to a heart chamber. FIG. 6 shows an embodiment of a
tensioning device 600 in a delivery configuration. The delivery
configuration of the device having distal and proximal anchors each
with four flexible arms in a radially compressed, folded
configuration while the anchors are within delivery catheter 630.
When the device is deployed from the delivery catheter, the arms
will self expand to a deployed configuration (as shown in FIGS. 1
& 2).
[0042] FIGS. 3 & 4 depict alternate embodiments of the
tensioning devices disclosed herein. The device 300 depicted in
FIG. 3 has a tension member 320 configured in a helical spring
shape and formed from wire or the like. The device includes a
proximal anchor 315 positioned adjacent to the proximal end of a
tension member 320, and a distal anchor 315 positioned adjacent to
the distal end of the tension member 315. Both the proximal and
distal anchor members have a plurality of arm segments 311, 312,
316, & 317 for resting against a heart chamber wall. At least
one embodiment of the current invention having arms similar to
those shown in FIG. 3, includes flexible arms.
[0043] The device 400 depicted in FIG. 4 has a tension member made
from some material of suitable elastic properties but not having a
helical spring type configuration. Embodiments similar to the
depicted embodiment can be made from elastic monofilament, braided
elastomeric thread, or the like. The device includes a proximal
anchor 415 positioned adjacent to the proximal end of a tension
member 420, and a distal anchor 410 positioned adjacent to the
distal end of the tension member. Both the proximal and distal
anchor members have a plurality of arms 411, 412, 416, & 417
for resting against a heart chamber wall, and the arms can be made
from a suitable flexible material.
[0044] FIG. 5 depicts another embodiment of the current invention.
As can be seen in FIG. 5, the device 500 includes distal and
proximal anchors 510, 515 having portions that are made from a
plurality of fibers braided into a tubular configuration. The
tubular braid anchors can be made from fibers comprising any
biocompatible material that will provide suitable strength and
flexibility. The tubular braided portion of the anchors for the
embodiment depicted in FIG. 5 surround anchor sections with a
plurality of arms similar to the arms of the anchors shown in the
embodiments of the invention depicted in FIGS. 1-4.
[0045] The tubular braided portion of the distal anchor 510
includes a fixed hub 561 that is attached to the distal portion of
the tension member and an inside hub 562 that moves freely along
the length of the helical spring tension member 520. The proximal
anchor 515 includes a fixed hub 567 that is attached to the
proximal portion of the tension member and an inside hub 566 that
moves freely along the length of the tension member. An anchor
adjustment chord 530 is routed through an eyelet 519 at the
proximal most end of the tension member and back through a delivery
catheter (not shown) to a clinician. While not depicted with the
devices shown in FIGS. 1-4, embodiments of devices similar to those
depicted do have an eyelet similar to eyelet 519 shown in FIG. 5.
When the tension device 500 is deployed, a clinician can apply
tension to the adjustment cord to keep the proximal end of the
device in the delivery catheter and keep the proximal anchor from
deploying within the heart chamber.
[0046] According to the current invention, there are a plurality of
ways to make the anchors assume a deployed configuration after
delivery. In one preferred embodiment, the anchors can be made from
a shape memory material and then pre-set in a deployment
configuration before being forced into, and restrained in, a
delivery configuration. In other embodiments of tension devices,
the anchors can be mechanically forced into the deployment
configuration after delivery to a heart chamber.
[0047] Referring to FIG. 5A, when the device depicted in FIG. 5 is
deployed and tension is applied, the arms of the anchor extend
outward to a deployment configuration while the center of the
braided portions expand radially to an essentially circular disc
around the arms. The figure shows the anchor in a slightly domed
state just as tension is starting to be applied. As the device
comes under the full tension load, the anchors are pulled flat into
a generally flat disc. Thus the arms provide support for the anchor
against the walls of the chamber. The combination of the arms and
the braided portion allows for an anchor that can rest solidly
against the walls of the heart and not migrate through the chamber
walls.
[0048] The anchors can be configured for catheter delivery to a
ventricle and then expanded to a generally planar deployment
configuration to rest against the septum or free wall of a heart.
In a delivery configuration, the tubular braided anchors have a
relatively small outer diameter to allow them to pass through a
delivery catheter or other delivery member. Once the anchors are
deployed, they can assume a deployment configuration where a
portion of the tubular braid expands radially outward such that the
deployed anchor has a larger outside diameter than it had in a
delivery configuration.
[0049] Referring now to FIG. 6, there is shown an embodiment of a
tensioning device (shown generally as 600) as disclosed herein,
that is slidably received within a lumen of delivery catheter 630
for delivery to and deployment at the treatment area. The delivery
catheter 630 comprises a guiding sheath 632, a piercing tube 634
having a beveled portion 635, a holding tube 636, and a push
cylinder 638. Piercing tube 634 is slidable within a lumen of
guiding sheath 632, holding tube 636 is slidable within a lumen of
piercing tube 634, and push cylinder 638 is slidable within a lumen
of holding tube 636. Thus, delivery catheter 630 comprises four
separate, concentric members, each slidable to be individually
extended or retracted as needed to deliver the device 600.
[0050] The device embodiment 600 depicted in FIG. 6 has a tension
member 620 with a distal anchor 610 and a proximal anchor 615. Each
anchor has four flexible arms that are collapsed into a delivery
configuration and the arms expand into a deployment configuration
when the tensioning device is expelled from the delivery catheter.
The device includes an adjustment member 630 that is routed through
an eyelet 619 at the proximal end of the tension member. During
deployment of the device, the clinician can use the adjustment
member to keep the proximal anchor from entering the ventricle when
the device is being deployed.
[0051] Guiding sheath 632 comprises a flexible, biocompatible
material such as polyurethane, polyethylene, nylon, fluoropolymers,
or the like Guiding sheath 632 has a preformed or steerable distal
tip that is capable of assuming a desired bend with respect to the
longitudinal axis of the sheath, for example, a ninety-degree
bend.
[0052] Piercing tube 634 comprises the same or a different
biocompatible material from that used to form guiding sheath 632.
In the present embodiment, the distal end of piercing tube 634 is
angle cut to form a sharp edge 635 able to pierce into or through
myocardial tissue. Thus, where a device of the current invention is
to be delivered transluminally, piercing tube 634 must be flexible
enough to be delivered through vasculature to the treatment area
while still rigid enough to pierce myocardial tissue.
[0053] Piercing tube 634 may include a stop collar (not shown) to
aid in positioning distal anchor by controlling the depth of
penetration of piercing tube 634 into the wall. A proximal portion
of stop collar may be attached to the outside surface of a distal
portion of piercing tube 634. One embodiment of a stop collar is
cylindrical and has longitudinal slots spaced around a distal
portion of the cylinder to form segments that are heat set or
otherwise set such that they flare out away from the longitudinal
axis of the cylinder when stop collar is released from guiding
sheath 632.
[0054] Holding tube 636 and push cylinder 638 also comprise one or
more biocompatible materials. Push cylinder 638 may be either a
hollow or a solid elongated cylinder. Both holding tube 636 and
push cylinder 638 must be flexible while still having sufficient
rigidity to exert force on a heart chamber wall or an anchor, as
described below.
[0055] Adjustment member 630 can be made from suitable
biocompatible chord that can be routed through the eyelet at the
end of the tension member such that both ends of the adjustment
member extend from the proximal end of the delivery catheter.
During deployment of the device, the clinician can apply a slight
tension to the adjustment member while pushing on the push cylinder
to expel the device from the catheter. This allows the clinician to
ensure that the proximal anchor will not be forced into the heart
chamber that is being treated. Once the anchor has been properly
deployed and the device is properly adjusted, the clinician can
pull on one of the free ends of the adjustment member and withdraw
the member through the eyelet and out of the delivery catheter.
[0056] FIG. 7 shows a device for treating mitral valve
regurgitation at an intermediate step in the deployment. FIG. 8
shows the device fully deployed, wherein the tension member 720 is
extended across a chamber of a heart, the proximal anchor 715 is
deployed against a first wall of the heart chamber, and the distal
anchor 710 is deployed against the exterior of a second wall of the
heart chamber. The device depicted in FIGS. 7 & 8 is the device
shown in FIGS. 1 & 2 and described above, chamber where the
device is deployed is the left ventricle, the first wall is the
septal wall between the right and left ventricles of the heart, and
the second wall is the left ventricular free wall.
[0057] When positioned across a heart chamber, the anchors and
tether are under continuously varying tension due to the motion of
the beating heart. To withstand this environment, the tension
member comprises an elastic, biocompatible, metallic or polymeric
material that combines elasticity, flexibility, high strength, and
high fatigue resistance. For example, the device may be formed
using metallic wire, metallic tubes, polymer braid, polymer thread,
elastomeric monofilament, elastomeric yam, etc, so long as the
material has suitable elastic properties to allow the tension
member to apply a continuous tension force between the two anchor
members.
[0058] In some embodiments, an antithrombotic component may be
included in the chemical composition of the material used to make
the tensioning device. Alternatively, an elastomeric, polymeric, or
metallic tether may be coated with a polymer that releases an
anticoagulant and thereby reduces the risk of thrombus formation.
If desired, additional therapeutic agents or combinations of agents
may be used, including antibiotics and anti-inflammatories. Other
embodiments of the devices disclosed herein can include a coating
or sleeve made from Dacron.RTM. fiber or the like.
[0059] To ensure proper positioning, it is desirable that
tensioning device be visible using fluoroscopy, echocardiography,
intravascular ultrasound, angioscopy, or another means of
visualization. Some embodiments of the devices disclosed herein can
be coated with echogenic materials and some devices can include
materials having a high X-ray attenuation coefficient (radiopaque
materials). The devices may be made in whole or in part from the
material, or they may be coated in whole or in part by radiopaque
materials. Alloys or plastics may include radiopaque components
that are integral to the materials. Examples of suitable radiopaque
material include, but are not limited to gold, tungsten, silver,
tantalum, iridium, platinum, barium sulfate and bismuth
sub-carbonate.
[0060] Referring again to FIG. 7, for delivery, the device is in a
configuration similar to that shown in FIG. 3. Tensioning device is
slidably received within a delivery catheter 730. The delivery
catheter 730 has the same components of the catheter depicted in
FIG. 3 and the delivery/positioning of the tensioning device shown
in FIG. 7 will be described using the terms used to describe the
components of the delivery catheter 330 shown in FIG. 3.
[0061] The arms of proximal anchor and distal anchor respectively,
start in a folded, radially compressed configuration. Proximal
anchor is positioned within the lumen of a holding tube while
distal anchor is positioned within the lumen of a piercing tube. A
push cylinder abuts the proximal end of proximal anchor. Holding
tube abuts the proximal end of distal anchor.
[0062] Delivery catheter carrying tensioning device is passed
through the venous system and into a patient's right ventricle.
This may be accomplished as shown in FIG. 7, in which delivery
catheter 730 has been inserted into either the jugular vein or the
subclavian vein and passed through superior vena cava 742 into
right atrium 744, and then passed through the tricuspid valve into
right ventricle 748. Alternatively, the catheter may be inserted
into the femoral vein and passed through the common iliac vein and
the inferior vena cava into the right atrium, then through the
tricuspid valve into the right ventricle. The procedure may be
visualized using fluoroscopy, echocardlography, intravascular
ultrasound, angioscopy, or other means of visualization.
[0063] The distal tip of delivery catheter 730 is positioned
against the right ventricular surface of the septum 750. The
delivery catheter then pierces the septal wall by extending
piercing tube beyond the distal end of guiding sheath until the
tube pierces through the septal wall.
[0064] The distal anchor 710 is then engaged with a second wall of
the heart chamber. In the depicted embodiment, the distal anchor
710 is expanded on the exterior surface of the myocardium and
engaged with the free wall of left ventricle 752. To accomplish
this, piercing tube is advanced across the left ventricle between
the papillary muscles and the chordae tendinae attached the mitral
valve 756 leaflets that separate the left ventricle 752 and the
left atrium 754. The piercing tube is allowed to pierce into the
free wall of left ventricle 752 and the guiding sheath and its
contents are advanced through the septal wall and across the left
ventricle.
[0065] Distal anchor 710 is then pushed out of piercing tube using
holding tube, at which time arms are permitted to expand away from
the body of distal anchor and fix the distal anchor firmly against
the exterior of the wall. In at least one embodiment of the current
invention, the anchor remains inside the pericardial membrane but
in other embodiments the anchor is outside of the pericardial
membrane such that the membrane is between the deployed anchor and
the myocardium. Alternatively, distal anchor 710 may be delivered
by extending piercing tube to penetrate through the free wall of
the left ventricle, and then retracting piercing tube while holding
distal anchor stationary with holding tube. Distal anchor is thus
released from the distal end of piercing tube and permitted to
self-expand.
[0066] Following deployment of the distal anchor, piercing tube is
withdrawn across the left ventricle, through the septal wall, and
into guiding sheath. The tension member, which links distal anchor
with proximal anchor, is allowed to slide out transverse the left
ventricle as piercing tube is withdrawn.
[0067] The proximal anchor is then deployed such that it engages
with the septal wall. To accomplish this, proximal anchor is pushed
out of holding tube using push cylinder, or holding tube is
withdrawn while proximal anchor is maintained stationary with push
cylinder. Proximal anchor is thus released from the distal end of
piercing tube and permitted to self-expand as seen in FIGS. 1 &
2. During the deployment of the device the adjustment member can be
used as described above to make sure that the proximal anchor is
not extended into the left ventricle.
[0068] Referring to FIG. 8, the deployment of the device is
complete, with the distal anchor 710 resting against the exterior
of the free wall 758 and the proximal anchor 715 resting against
the septal wall in the right ventricle. The tension member 720
extends across the left ventricle between the papillary muscles 755
& 753 and the chordae tendinae.
[0069] In order to resist excessive elongation during diastole, the
material used should stiffen dramatically when elongated. During
systole, the tension member should again be elastic to as to
recover or recoil. In some embodiments of the invention, it may be
desirable to have some pre-load on the tension member so that the
anchors remain seated and so that no slack develops in the tether.
FIG. 9 shows an ideal response curve for the materials used to make
tensioning devices of the current invention.
[0070] Referring to FIG. 10, a block diagram shows the steps of one
method of using the devices disclosed herein. First, the treating
clinician determines the desired wall tension of the heart, the
length of device needed to appropriately reduce the distance
between the septal wall and the free wall of the heart chamber, and
the device characteristics as described above (block 1001). The
device is then delivered to a position adjacent a first wall of the
heart chamber (block 1002), which can be the septal wall as shown
and described herein, or the device can also be delivered from the
exterior of the heart using surgical techniques that are known in
the art of cardiac surgery or even a catheter from a vessel that is
exterior to the chamber being altered. The fist wall is pierced
(block 1005) and the second wall is pierced, so that a distal
anchor can be engaged with the second wall (block 1007). A proximal
anchor is then engaged with the first wall of the heart (block
1009) and the delivery device is removed. As a result of shortening
the lateral space between the free wall and the septal wall, and
reducing the wall tension, the geometry of the heart has been
altered and mitral regurgitation is reduced.
[0071] The tension member is made from a material having suitable
elasticity and constructed in a suitable configuration such that it
applies a constant tension force between the two anchors to draw
the walls of the left ventricle together and reduces both the
radial tension on and the radial dimension of the mitral valve 754,
thus improving coaption of the valve leaflets and reducing
regurgitation. The tension member elongates and contracts (flexes)
in response to a heartbeat when the anchors are secured and the
tension member positioned across the heart chamber. This provides a
shock absorbing effect that helps to protect the tensioning device
from fatigue and reduces localized compressive pressure on tissue
against which the anchors rest. In some embodiments of the
invention, the anchors can also include flexing elements to further
reduce fatigue and reduce pressure on the tissue.
[0072] The tensioning device may be placed in close proximity to
the mitral valve, so that when the tension member contracts such
that the distance between the proximal and distal anchors is
adjusted, the outer cardiac wall is drawn toward the septal wall
such that the anterior and posterior leaflets of the mitral valve
are drawn together, thus reducing regurgitation. Alternatively, the
device may be positioned across the left ventricle at an angle such
that, for example, only one end of the device is anchored as close
to the mitral valve annulus as possible.
[0073] Two or more devices may also be placed across the left
ventricle in parallel, crisscrossing, or in other patterns as
believed by the treating clinician to best achieve the desired
result of radially compressing or relieving tension from the mitral
valve. Alternatively, or in addition to ventricular placement, a
tensioning device of the invention may be deployed across the left
atrium, as approached from the right atrium, to radially compress
or relieve tension from the mitral valve.
[0074] While several embodiments of the invention have been
disclosed herein, various changes and modifications can be made
without departing from the spirit and scope of the invention. The
scope of the invention is indicated in the appended claims, and all
changes and modifications that come within the meaning and range of
equivalents are intended to be embraced therein.
* * * * *